Great Britain will face second seeds Croatia in the Fed Cup promotion play-off on Saturday.
Heather Watson and Johanna Konta won their singles matches against Turkey to take an unassailable lead in their final best-of-three group match.
Jocelyn Rae and Laura Robson completed a 3-0 sweep in the doubles, with Anne Keothavong's team topping Group C.
Their play-off place was already sealed after Latvia earlier beat Portugal in Britain's group.
Watson powered Great Britain to a 1-0 lead by beating 163rd-ranked Ipek Soylu 6-0 6-1.
British number one Konta then overcame an early wobble to beat world number 86 Cagla Buyukakcay 5-7 6-4 6-3 in the second singles match.
"I didn't get the chance to play Fed Cup last year, but from the very beginning of the season I was clear that I wanted it to be part of my schedule," Konta told British Tennis.
"I think whenever I get an opportunity to represent Great Britain in a team environment, I look to take it."
Rae and Robson then breezed to a 6-2 6-2 victory over Ayla Aksu and Pemra Ozgen in 58 minutes to ensure Great Britain ended the group stages unbeaten.
Fed Cup format
Unlike the men's team competition, the Davis Cup, which has a World Group of 16 nations, the Fed Cup divides its top teams into two groups of eight - World Group I and World Group II.
The 91 nations outside the top tiers are divided into three regional zones and Britain have one chance per year to escape - a format that hugely frustrated former captain Judy Murray.
The Europe/Africa Group I event, which this year takes place in Estonia, has 14 teams divided into groups, with Poland, Croatia, Britain and Serbia the seeded nations.
Four group winners will progress to promotion play-offs on Saturday, and two nations will then qualify for World Group II play-offs in April - which could see Britain given a home Fed Cup tie for the first time since 1993.
They fell at the same stage in 2012 and 2013 - away ties in Sweden and Argentina - under the captaincy of Judy Murray.
|FED CUP EUROPE/AFRICA GROUP I|
|GROUP A||GROUP B||GROUP C||GROUP D|