Warunki płatności: 10% zaliczka, 80% po podpisaniu protokołu końcowej akceptacji, 10% rata gwarancyjna. Kary umowne nie mogą...
http://tinyurl.com/on6hrqp

...10% Advance, 10% Retention & balance 80%.
http://tinyurl.com/oau2r9e

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Note added at 2 hrs (2013-12-08 20:31:14 GMT)
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Można dodać "final": final retention payment.

The employer [tu: zleceniodawca] will usually hold on to, or retain, the agreed amount (say 10%) from each payment becoming due to the contractor throughout the...
The other 10% is paid when the retention payment terms have been met...
One service related invoice will be booked with 90% payment and 10% retention.
...a 10% retention rate for both main contractor and subcontractors....
...receipt of final retention payment with any applicable warranty information.
Final Payment: Providing no labor or payment claims are received, the 10% retention payment may be released after the following date:
Q. When will I receive my retention payment? (final 10% of the contract); A. After we have received all final material releases from your suppliers or...
...delivery and completion of which is linked to a final retention payment equal to 10%...
Resolution 12/13-13 accepts the work as complete and provides for a retention payment of $4,480, which is 10% of the contract amount.
http://tinyurl.com/oau2r9e

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Note added at 2 hrs (2013-12-08 20:50:12 GMT)
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Może też być samo "retention", "payment retention", "payment/installment retained as security", "holdback payment" ("payment holdback") - wszystko zależy od rzeczywistego kontekstu (nie został podany).

Tu podobne pytanie: http://www.proz.com/kudoz/4338395 .

...10% of all the payment made will be retained as security which will be...
The remaining balance is retained as security until all of the receivables are...
...shall be retained as security deposit and paid at the end of the...
...balance 10% shall be retained as security which shall be released after the...
... to be retained as security for completion of all...
http://tinyurl.com/q66uzff

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Note added at 4 hrs (2013-12-08 22:38:32 GMT)
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W podanym RZECZYWISTYM kontekście:
zatrzymanej jako rata gwarancyjna - retained as security (portion)

I zrobiłbym tak:
Od tak wyliczonej kwoty należy odjąc xxx, retained as security, co stanowi 5% sumy wyliczonej wg. uzgodnionego wskaźnika, która zostanie wypłacona...