Deeming rates are used to estimate how much some pensioners earn on their financial investments, including pensioners and nearly 350,000 people receiving other income-tested payments.

The deeming rate on the first $51,800 of a single pensioner's financial investments - and the first $86,200 of a couple's - will drop from 1.75 per cent to 1 per cent.

The deeming rate for balances above those amounts will go from 3.25 per cent down to 3 per cent.

Only four electorate have more than 10 000 pensioners affected by deeming rates and Cowper tops the lot with 11 528 people who will see $800 more a year, or couples can expect to receive $1000 more in their pockets each year.

Member for Cowper Pat Conaghan said it was good news for locals.

"About a quarter of all ages pensioners are affected by deeming rates but the Cowper electorate has the biggest numbers in the country," Mr Conaghan said.

Mr Conaghan described deeming rates as a simple calculation tool based on inputs like interest rates and and share market returns.

He said deeming rates were designed to make things simpler for pensioners.

"Without deeming rates, Centrelink calculates how much a pensioner is deemed to have earned from their investments and adjusts fortnightly pension payments to reflect this deemed income," Mr Conaghan said.

The Reserve Bank's two consecutive interest rate cuts have taken its cash rate to a record low of one per cent.

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