“Polymarket average price including fees” can refer to a different quantity from average execution price. One measures what you paid for matched shares; the other also allocates identified fees across those shares.
Before comparing two entry figures, establish what each includes. A difference is something to reconcile—not automatic proof of a fee, slippage or an error.
Start with five separate amounts
For this guide, use these bookkeeping definitions. They are not claims about the meaning of any particular interface label.
| Item | What to record |
|---|---|
| Shares acquired | The matched shares covered by the purchase records you are reviewing |
| Purchase value | The sum of matched share quantities multiplied by their execution prices, before separately identified charges |
| Evidenced charges | Venue fees and applicable third-party charges supported by records and relevant disclosures |
| Total debit | The observed amount debited for the same purchase scope, if you can establish it |
| Unexplained difference | The amount left after subtracting purchase value and evidenced charges from total debit |
Keep the currency, purchase scope and share count consistent. Do not compare one order's purchase value with a broader balance change unless you can account for everything else in that change.
A hypothetical purchase, worked through
Illustration only: these figures are invented for arithmetic, not a Polymarket fee schedule or a real transaction. Assume all charges in this example are recorded in dollars, separately from purchase value.
You acquire:
- 60 shares at $0.40: $24.00 of purchase value.
- 40 shares at $0.45: $18.00 of purchase value.
That gives you 100 shares with a combined purchase value of $42.00. Records also establish a $0.60 venue charge and a $0.20 interface charge attributable to this purchase. The observed total debit is $43.00.
Average execution price
Divide purchase value by matched shares:
$42.00 ÷ 100 = $0.420 per share.
This is a quantity-weighted average. Simply averaging the two execution prices would ignore that more shares were bought at $0.40.
Unit cost including evidenced fees
Add the identified fees before dividing:
($42.00 + $0.60 + $0.20) ÷ 100 = $0.428 per share.
A precise label is “unit cost including evidenced venue and interface fees.” It states which costs are included without claiming every possible cost has been established.
Total debit and the unresolved amount
The documented components add up to $42.80, but the observed debit is $43.00:
$43.00 − $42.80 = $0.20 unexplained.
Dividing total debit by shares gives $0.430 per share. That is a debit-per-share calculation—not evidence that the entire difference from execution price consists of fees.
Keep the $0.20 unresolved until records establish its cause. Do not invent a charge to make the worksheet balance.
Venue fees and interface charges are different layers
The Polymarket fee documentation is the relevant source for venue fee rules. It does not, by itself, define every third-party interface's charges or explain every displayed “average price” field.
If you use a third-party interface, review its applicable fee disclosure separately and connect any charge to the purchase records. A zero venue fee, where verified as applicable, would not by itself establish that using an interface costs nothing.
Likewise, a vendor disclosure alone does not prove that a particular charge occurred on your purchase. You need both the applicable terms and evidence of the amount charged.
This guide does not reproduce a venue fee formula or quote a current rate. Do not treat a fee-formula coefficient as a flat percentage of spend without verifying the formula and its inputs.
A quick reconciliation checklist
- Define the scope. Identify the purchase records and currency being compared.
- Use matched quantities. Calculate purchase value from the shares actually acquired, not the quantity you intended to buy.
- Separate evidence from estimates. Mark each charge as documented, estimated or unknown. Missing evidence does not mean zero.
- Avoid double-counting. Check whether an amount already includes a charge before adding it again.
- Compare with an attributable debit. If you only have a broader balance change, mark the purchase's total debit as unconfirmed.
- Keep a residual. Record any remaining difference without assigning a cause prematurely.
Compare definitions before comparing numbers
Average execution price, unit cost including identified fees, and total debit per share can all be useful. They answer different questions. A meaningful comparison uses the same share scope and cost components on both sides.
TickBetter is PRE-ALPHA and currently in development, with a focus on execution clarity. Keep this checklist handy when reviewing your own records; it does not depend on a live TickBetter tool.